Battery Base

FIG. 1 is a perspective view of a battery base showing my new design; FIG. 2 is a front elevational view thereof; FIG. 3 is a top plan view thereof; FIG. 4 is a left side elevational view thereof; FIG. 5 is a rear elevational view thereof; FIG. 6 is a right side elevational view thereof; and, FIG. 7 is a bottom plan view thereof. The broken lines in the drawings depict portions of the battery base that form no part of the claimed design.